1. Field of the Invention
This invention relates to data processing systems. More particularly, this invention relates to data processing systems providing tracing mechanisms to enable data accesses via multiple data access instructions to be traced.
2. Description of the Prior Art
As data processing systems increase in complexity whilst it is desired to also reduce development time for new systems, there is a need to improve the debug and tracing tools and mechanisms that may be used within the development of data processing systems. Tracing the activity of a data processing system whereby a trace stream is generated including data representing the step-by-step activity in the system is a highly useful tool in system development. However, with the general increase in processing speeds, the speed at which trace data must be captured is also increased when it is desired to trace the real time operation of the system being developed. Accordingly, as well as off-chip tracing mechanisms for capturing and analysing trace data, increased amounts of tracing functionality are being placed on-chip. Examples of such on-chip tracing mechanisms are the Embedded Trace Macrocells provided by ARM Limited, Cambridge, England in association with their ARM7 and ARM9 processors.
It is known to provide tracing and debugging mechanisms incorporating trigger points that serve to control the debugging and tracing operation, such as starting or stopping debugging upon access to a particular register, address or data value. Such mechanisms are very useful for diagnosing specific parts of a system or types of behaviour. As an example, if a particular system bug is associated with exception behaviour, then tracing the full operation of the system would produce an inconveniently large volume of data when what was really required was tracing of the exception behaviour with this being triggered upon access to the appropriate exception handling vector.